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What is the use of heading bug?
When I started searching for Heading Bug (other bugs like altitude, speed bugs), I didn't get much clear idea about it. Usually this is displayed on Horizontal Situation Indicator display on the direction of wind (calculated based on wind direction, speed?). This heading bug can be selected to a value by pilots during flight.

What is the use of heading bug?
how heading bug is calculated?
what's the significance of heading bug?

Bugs simply make instruments easier to read with a very quick glance.
If I need to steer exactly 162 degrees, which is easier?  To read where the needle is pointing or just see if the needle is pointing to the bug which I manually set to 162 degrees?
The bugs are set by rotating knobs on the gauges.  Here, the heading bug knob is in the lower right corner.

The way I often use it is to turn onto the next heading required according to my plan, then set the bug to that heading so that I can simply glance at the needle (still pointing to the bug, good) to keep me on course.
Other uses:

If ATC gives you a "next heading", you will read back the instruction, then you can set the bug to that next heading so that a), you don't forget it and need to call back and b) can simply turn onto the bug when it's time to turn.
Set it to the departure runway heading on take off.  To "fly runway heading", just keep the bug at the top of the gauge.
On arrival, set it to the landing runway heading.
As a "gross error" check.  You would not believe how many inexperienced pilots set off in entirely the wrong direction.  As well as setting the heading bug to "first leg of the plan", you check this along with "and the road should be on my left with the river on my right".

On some simple autopilot systems, the autopilot follows the altitude and heading bugs rather than having controls for these settings on the autopilot itself.

@Simon why would I set bug when I know which direction I wants go? I can directly use the Heading instead of bug.

@Lucky As I said, it's just easier to see if the needle points to the bug rather than to read the value.  If I don't set the bug, then everything still works, I just need to read a little more carefully to make sure I stay on track.

@Simon would you do some math for calculating the Bug? will this be used when cross wind is applied? How this will be used in Autopilot mode to steer the plane? or just as you said pilot will monitor heading w.r.t bug even when it is under autopilot control? Also same logic applies to other Bugs too?

This is a very good answer. Just marked it up. When you are piloting an aircraft  you have lots of things to think about. The heading bug is good to remember the heading you are supposed to be flying especially as you don't want to go in the wrong direction or look bad in front of ATC. When you have a lot to think about is very easy to make a mistake. So if you always set the bug its one less thing to remember. There are many reasons why you would set it, although it sounds to me that how you arrive at your heading yourself might be a whole new question about VFR navigation. Hope this helps.

@Lucky Those are good questions but, I think you are better asking a new question for that.  This question is "what is it", a new good question would be "how to use it, especially when thinking about wind.  The short answer is that heading is the direction that the aircraft is pointing.  "Track" is the direction that the aircraft moves across the ground.  If you are taking wind ("drift") into account, then the heading bug will not be set to the direction you want to move across the ground.  This topic is more about VFR navigation than the heading bug itself.

I believe it's not just simple autopilots, but all or most of them. Advanced autopilot will have more modes, but one of them will still be following the heading bug. And even if the setting knob moves to the autopilot panel, it is still the one indicated by heading bug (multiple selected headings would just be confusing).

@JanHudec I just meant that the "heading bug" on a complex AP is set through the MCP, or similar control unit, rather than on the gauge.

regarding item #3 "On arrival," if its VFR, I will use the GPS's OBS mode  set to the runway heading to track the extended centerline, and the bug for my intercept heading. just a thought.


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Is there a 'common courtesy' distance that should be complied with when initiating contact with ATC for class D airspace?
Some background: I'm a student pilot preparing for an upcoming stage check involving XC diversions and have been trying to visualize different scenarios of what I'd need to do when diverting. One case I was thinking about is if you're flying, say, directly above class D airspace (in this example, maybe 3500 ft) and intend to divert there, is it considered acceptable to call the tower while directly overhead, or are you expected to be further out laterally before making an initial call?
I apologize if this is a pretty unusual question, but I want to make sure I'm not violating any unspoken rules.
To illustrate what I mean, assume I want to land at KLGB. Should I call overhead (red dot) or is it advised to get some lateral distance first (to blue dot) and then call?

To answer the question in the title, the AIM 4-3-2 says:

When operating at an airport where traffic control is being exercised
by a control tower, pilots are required to maintain two-way radio
contact with the tower while operating within the Class B, Class C,
and Class D surface area unless the tower authorizes otherwise.
Initial callup should be made about 15 miles from the airport.

FWIW, I fly out of a class D and usually call 10 miles out, which gives plenty of time to contact ATC. As always, use some judgement: if the airspace is busy and the radio traffic is heavy then call further out. If it's very quiet then calling closer to the airport should be fine.
All that said, the body of your question is about being directly overhead the field. That seems like an unusual scenario (to me) but there's nothing wrong or problematic about it. I'd just call the tower, tell them where I am and that I intend to land, and let them tell me how and where to join the pattern. I can think of two practical points that might come up:

They might assume you have some sort of emergency, so be ready to tell them you don't (unless of course that is your reason for landing there!)
They might give you instructions to join the pattern that are difficult to comply with because they don't know what you and your aircraft are capable of. Or they might ask you how you'd like to join. Have a plan, be ready to say "unable" if you aren't comfortable with their instructions, and if necessary just tell ATC you need to fly some distance away from the airport to get down to pattern altitude.

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Do airways with multiple numbers (e.g., J89-101) imply combined segments?
On SkyVector, I see many airways with 'multiple' names such as J16-36 or even J89-94-100-128. I can't find any information on how to interpret these names.
I'm guessing it's a convention to say that for some portion of the airways, J89 and J94 overlap - but presumably it's still valid to simply route along J94 including those shared segments?

Example near KORD

Yes, from your example J34-68-538 are jet routes that share a segment and aircraft on different routes may travel the same segments between waypoints. A complete explanation is in the FAA's Aeronautical Chart User Guide.

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What is the meaning of “American 755, turn right, heading 320"?
I am studying a text entitled Unmanned Aircraft Systems. How can we simplify the instruction in quotes so that it is more understandable and can be understood by a nontechnical. Please note I am not seeking to know all technical jargon of routing aircraft, rather to get what a pilot is told with this instruction to do.

Ideally, the communication process includes three parts: the
  initial call, readback, and hearback. For example, an ATCO would issue an instruction “American 755, turn right, heading 320.” Pilots onboard the aircraft would respond, or readback the message “Right, heading 320, American 755.”

I'm on the fence as to whether this question is a duplicate of:  http://aviation.stackexchange.com/q/8000/167

That too has great answers relating to this.

It is quite simple if you look into the answer linked by Steve V. to understand what the headings are. Here is a simple example: aircraft flies at 290. Controller instructs right turn to 320. The image below shows how should the aircraft turn. Heading is on top and on the orange "bug". (Needle shows track but you can safely ignore it for this example).

But here is a subtle case: if the aircraft flies on a heading of let's say 030 and the crew is instructed to turn right heading 320, then they should perform a 290 degrees turn to the right to meet heading 320.

This might not be obvious at first sight as it seems awkward, but it's critical in air traffic control.
Notes for the images: Compass is set to show "head up" ie the current heading of the aircraft on top and not "north up". Also the compass rose for brevity does not depict degrees but tens of degrees. So "15" stands for 150 degrees. Images source: own work.

Yeah it is confusing, I cannot match it with trigonometric circle or a simple watch. I might need to do some study on Wikipedia about this.

@JasonStack May I ask what is confusing? Bear in mind that in trigonometric circle, angle increases counterclockwise while in a compass heading increases clockwise.

Ok, how many degrees are there in the circle in total and why doesn't 0 start from a position corresponding to North (clock 0)?

@JasonStack 360 degrees and 0 is not on top because compass is set to "head up" not "north up". Actually I will incorporate that last part in the answer.

I like your image source, well done!

@JasonStack - in both illustrations, look for the 0: that's pointing North. There are 360 degrees in the circle, but the compass shows only the first two digits. So 27 is 270 degrees from North, i.e., West. The compass is showing the plane's heading at the top. The first one, for example, shows a plane whose heading is 290 degrees: that's the 290 at the top of the circle. Doing it that way makes it easier to picture what's going on, once you've gotten used to it.

@DeltaLima Heh, thanks. FYI, the images come from the pseudopilot of DARSSY, the simulator I've developed.

Note that compass on ships and in aircraft is always heading up/forward, that is the compass rose rotates with the needle, because it is simpler to steer according to such compass.

American 755, turn right, heading 320.

Aviation phraseology is direct, specific, and concise. The three items here:

The controller is instructing the aircraft identified as American 755
to make a right turn
such that they maintain a heading (direction) of 320 degrees (5 degrees north of north-west).

Though you may not be interested right now, at some level you might have to get technical, as communication involves defining terms :)
In case you are interested, for references and further reading see this page from the FAA. Especially of note:

Pilot/Controller Glossary - contains definitions for radio communications.
Aeronautical Information Manual - contains instructions for pilots.
JO 7110.65 - (more technical) the handbook for controllers. Everything they say should be in there.

It is worth noting that heading means a direction the aircraft is to point  (along the aircraft longitudinal axis) relative to the magnetic compass as opposed to: a "true" heading relative to geographical north; a direction the aircraft is to track; or a course to be flown. The differences are important and may not be obvious to those not in the know.

The basic answer is that the controller is instructing American 755 to turn right in order to point the airplane a direction which is 320 degrees clockwise from due north (basically northwest)
For the specifics of what a "heading" is, see this excellent answer (with pictures!).

'American' is the callsign of American Airlines and '755' is the flight number.Here the plane is being intructed by the Air Traffic Control to make a right turn until they are pointing towards the 320 degrees mark on their heading indicator or the compass.

It doesn't add to the already numerous answers, is it?

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What is the purpose of this helicopter fin antenna?
I'm an airplane guy, but I've got a quick helicopter question. I've seen a few helicopters with what seems to be a fin shaped antenna on the middle of the fuselage just above the windshield. I've also seen them just below the cockpit. And sometimes there's two antennas, one above, and one below.

(source)
Just curious what its purpose is?
The antenne balise de detresse is the one I'm curious about:

To be clear, there is an antenna behind the wire cutter (hard to see) that is the antenne balise de detresse or distress beacon antenna or ELT antenna.

Antenne balise de detresse translates to "Emergency beacon Antenna" It's unclear wether it is for receiving or emitting tho.

It can be quite difficult to see as the big fin in the first photo is a wire cutter and it seems that the arrow points to that.
The second photo shows it a little more clearly.  It is a wire cutter.

Thanks for the information about the wire cutter. Youtube.

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Are aircraft designers in demand in Canada/US in near future?
I am a high school graduate who loves aircraft designing and are aiming to get into universities that has aerospace engineering majors. However, I have heard people saying that since aircraft companies will keep their designers in the company until they retire, there is little oppurtunity to get into this industry. Is is true? If it is not, then where can I find more oppurtunities?

I wonder if this might get a better reply in http://engineering.stackexchange.com/ by the way? Also I would guess you'll find a lot of people in the aviation industry aren't specialist aeros, but more general engineers who specialised later.

Maybe PPRuNe could be a good place to ask for that too.

It is not necessary to have an Aerospace Engineering degree to get a foothold into the engineering side of aviation. Most of the major aircraft companies operate on a very long design cycle, and maintaining employees with specialty engineering disciplines is not cost effective. While there will likely always be SOME aerospace engineers employed by companies like Boeing, the majority of their engineers are Mechanical, Electrical, Industrial, Manufacturing, and Tooling engineers.
Mechanical engineering, in particular, would open you up to a much broader base of job opportunities all over, both in and out of the aerospace industries.
An invaluable resource for you as you look at your choices, is the Occupational Outlook Handbook, created by the US Bureau of Labor Statistics. In it is listed expected salaries, expected job growth opportunities, how competitive the field is, etc. For Aerospace engineering, for example, http://www.bls.gov/ooh/architecture-and-engineering/aerospace-engineers.htm indicates that the market is expected to decline by an average rate of 2% over the course of 2014-2024. This would indicate that Aerospace Engineers are not in high demand. However, Mechanical Engineers are expected to grow by an average of 5% in the same time period.


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What's an "outrigger" for parking aircraft on a carrier?
In this picture of the USS Intrepid (CV-11), there appears to be an aircraft parked with the tail hanging off the deck:

(Source)
The caption gives a clue:

The U.S. Navy aircraft carrier USS Intrepid (CV-11) operating in the Philippine Sea in November 1944. Note the Grumman F6F Hellcat fighter parked on an outrigger forward of her island.

This "outrigger" appears to be some sort of triangular structure to partially support the aircraft's weight:

Further research, however, turns up no more information about this "outrigger." So:

What exactly was this device?
How was it used?
What's its history?
Who manufactured it?

I would not want to be sitting in that aircraft!

You can see it a bit better in this picture:

(Source)

In order to save deck space for operations, the smaller escort
  carriers like HMS Khedive used outriggers. The tail wheel is first
  affixed and locked to the rigger trolley and then the aircraft is
  pushed outwards and the wheels heavily chocked fore and aft of the
  wheels. Here one of Khedive’s Corsairs demonstrates the concept
  perfectly. Note that the Corsair has Type C roundels, indicating it is
  in the European theatre of operations.

They were effectively a simple way to save deck space with out enlarging the deck. There is another decent pic here and some spitfires on outriggers here
Based on the info here they can be found as far back as the late thirties

It represents an F4B-4 positioned on an experimental outrigger aboard
  the USS Saratoga during the late 1930s. The Saratoga and several other
  aircraft carriers were selected to try out different types of deck
  outriggers for the Navy in the interwar era.

How does the aircraft get parked and unparked?

@built1n if you look closely at the pic the rear wheel is on a small slider. I see no reason why its any more complicated as pulling the aircraft forward. This is likely why the main wheels remain on the deck.

That makes sense. Is there any more to be found on the origins of the idea, and specifics about manufacturing, etc?

@built1n thats all I could find. You could try contacting the Smithsonian but it looks like an I-Beam hanging off the deck with a roller on it so I'm not sure what you are looking for beyond that. Considering the era they date from digital documentation is unlikely to be easily found. Construction on the Saratoga started almost exactly 100 years ago and its possible the ship yard that did the carrier conversion added these.


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Can Anyone Fly A Plane?
Have it ever happened that the flight attendants asked the most wanted and feared question of all flight-simmers out there: "Can Anyone Fly A Plane?"
My question is for events when all the pilots was incapacitated, and someone who in not a qualified pilot landed the plane.

Only in the movies.  And then Kurt Russell steps in to save the day.  Far more likely to ask for a Doctor to help with another passenger.

@CrossRoads How do you know that? It has actually happened.

That's why I commented, vs answered.  If there's a flight attendant, there's usually a first officer - guess who'd be flying then?

It actually gets said as "any non-revenue pilots, please push your call button".  If you heard it, you'd disregard it as technobabble, but it's a dogwhistle to pilots with any experience.


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Obtaining Captain's name on historical flights?
Is it possible to find out the name of the Captain on a previous flight?

Generally, no.  As a matter of protecting employees' privacy, that sort of information isn't typically made available beyond what a passenger may notice (nametags) or remember from a PA ("This is Captain Smith...").
In an unusual situation, it might be possible to get a name by contacting the airline, but it's probably unlikely that you'd get an answer back unless the pilot happened to call or write back to you.  Which could happen, but not often.


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Why is pitch measured with respect to the horizon and not the ground?
Why is the pitch measured with respect to the horizon and not the ground? How different are the angles between the ground and the horizon? Would it be possible to fly with an attitude indicator that indicated pitch with respect to ground rather than horizon? What does it mean when you have a 0 degree pitch with respect to the horizon? What, exactly, are you flying towards in that case?
I've always had a hard time understanding this. Thanks for your time.

If you were flying over steeply sloped ground, what would you want the pitch angle to show?   Pitch is related to the aircraft's passage through the air, not to the ground.  Think of it this way.  Pitch is related to angle of attack which is related to lift.  Lift counters gravity which always acts vertically downwards, perpendicular to the horizontal (the horizon) and not to the ground underneath which could be doing anything.

So if the Earth were perfectly spherical pitch with respect to the horizon and ground would be the same thing?

At the microscopic level of an aircraft flying over it, yes.  It assumes that the world is flat.  If the world was a perfect sphere, then the pitch would be constantly changing but by such a tiny amount, that the changes would just be "noise" in everything else that affects pitch.

I should have phrased that better. I mean in the perfectly spherical Earth sense of the word. If that was the case would the angle between the velocity vector of the plane and the horizon be the same as the angle between the velocity vector of the plane and the ground?

Take a line directly down to the center of the earth from the aircraft. where the aircraft is on this line, construct a plane that is perpendicular to this line. That plane (no pun intended) is the "horizon".

@Simon - that sounds like a very simple, yet valid answer, to me!

@Simon It's important to properly differentiate between pitch and angle of attack, though. Pitch is defined as the angle between body axis and horizontal, it is thus the angle between local gravity vector and body axis minus 90 degrees. Angle of attack is the angle between body axis and air flow. This is the same as pitch angle only in steady level flight without wind.Consider a modern airliner on approach. Often their pitch is nearly level, while the angle of attack is greater; as they are descending, the air flow "hits them from below".

@CptReynolds I'm a pilot!  I am fully aware of the difference between pitch and angle of attack but for a simple explanation, where I say that they are related, it will suffice.

@Simon My apologies, I didn't mean to be patronising. It's an easy mistake which many people make (not meaning you!), and all I was trying to do is to ensure this thread helps to dispel the common misconception. No offence!

Pitch is measured with respect to a plane orthogonal to the local weight¹ force, which is properly called the horizontal.
That is used because:

It is equipotential plane of the gravitational field. Moving around it won't change your potential energy.
Is always well defined.
Is smooth and locally flat (it is still a spherical surface globally, of course).
Can be measured by averaging inertial forces on board without external reference.

It is called simply horizon, presumably because looking at the horizon is the easiest way to find that plane by human senses.
Using ground, which is not flat, as reference wouldn't work. Aircraft need to fly mostly along the equipotential plane, because climbing to a higher one requires adding more energy by the engines and descending below means the aircraft accelerates and needs to dissipate (= waste) the energy. So following terrain would require quite a bit more energy than flying horizontal. Plus it would be very complicated.

¹ By weight I mean the sum of gravity and centrifugal force in the reference frame rotating with Earth.

Follow up question: how does a plane stay on that equipotential plane? If the lift force and gravity force cancel, then Newton's second law would seem to imply that the plane will move in the same direction it was previously moving, meaning the Earth would curve away from it and the plane would seem to ascend. Is there a constant correction for this, or is the lift on the plane made just right that the plane is constantly "falling," keeping it in circular motion?

@Dargscisyhp See this question over at Physics.SE. In short, they don't cancel. But really, your altitude will vary a lot more due to local winds and non-perfect control inputs - the curvature of the earth is negligible compared to that.

Heh, I actually asked that question. I'm not sure I got a consensus there and a couple of people suggested that physics.se was not the right place to ask.

@sanchises, That question is about including the centrifugal force due to Earth rotation and I intentionally said weight, not gravity, to include it.

@Dargscisyhp, If you perfectly balanced the plane to make it fly straight (in the reference frame rotating with Earth; we are including the centrifugal force by referring to weight), the lift would initially cancel each other, but the weight would slowly rotate, so after a bit the forces would no longer cancel perfectly, but instead add up to a small aft force. And that would slow the plane, exactly as expected from conservation of energy. The pilots (or autopilot) need to maintain the correct level by rotating the lift correspondingly.

@sanchises, No, weight is correct. General relativity says that "effect of homogeneous gravitational field is indistinguishable from effect of accelerating reference frame", so there is no way to distinguish the forces by local measurement. Yes, weight does not point to the centre of Earth, but it is what defines the equipotential surface followed by water level, and also ground, because rock is soft enough to behave pretty much as liquid on the planetary scale. I.e. Earth is not a sphere, it is slightly flattened and the centrifugal force is the reason.

"It is equipotential plane of the gravitational field. Moving around it won't change your potential energy". At a simplified level yes, but actually the equipotential surface is the geoid.

@mins, yes, the proper name of the "slightly flattened" thing is geoid. Calling it equipotential surface of the "gravitational" field is slightly misleading, because it includes the effect of rotation (I am not sure with the proper terminology in English (I am not native speaker), but believe this is nevertheless the standard term as there don't seem to be specific terms for distinguishing the cases).

@sanchises, the reason to use gyroscope is to separate out the inertial forces from the aircraft's own motion as that is not possible with local measurement either, so the gyroscope provides enough non-locality for that. It still does not separate out the effect of rotation of Earth itself, nor could it, nor does it intend to.

See this for additional details (surely pedantic here, this is just for the sake of curiosity). The slightly flattened thing should be the ellipsoid of reference. The potential is greatly affected by the mountainous masses (or the lack of rocks in abyssal trenches), hence the geoid undulations.

@JanHudec Ah, like so - I thought you were referring to the instantaneous weight vector which varies with the slightest gust of wind, but if you are referring to the average (non-instantaneous) weight vector, then yes, I fully agree. I'll clean up after me in the comment section :)

Your question seems to boil down to the following:
Assuming that the earth is a perfect sphere, why does the virtual horizon (i.e., the pitch indicator) point to the horizon? The answer is, it doesn't.
Pitch is determined with gravity, which always 'points' to the center of the earth. The virtual horizon you see on your pitch indicator is always at an angle of 90° (i.e., a straight angle) from that, and only points to the actual horizon in case you were exactly on the ground. This difference is negligible for normal flight (which happens in the very lowest part of the atmosphere). The following is only to demonstrate what is actually happening.

In the above picture, I drew an exaggerated version of what you mean. The red line points to the center of the earth (so, where gravity points), and is the reference of your pitch indicator. The green line is what you will see on your pitch indicator. The blue line is where you actually see the horizon. They don't match up, and that's fine.
A pilot really doesn't care where the horizon is. He cares about maintaining altitude, ascending or descending. Maintaining altitude is done by keeping the airplane level with respect to the center of the Earth, in which case he will make a complete circle around the earth since his velocity vector is always perpendicular to the center of the Earth. Ascending and descending is done by having the pitch above or below this.
From the picture you can see that if the virtual horizon were to point to the actual horizon, you would eventually impact the ground - on a perfectly smooth sphere, it would be a smooth landing too. I guess there's a reason they call it the virtual horizon, eh?

Good point that the actual horizon isn't the same thing as level / horizontal.

An airplane needs to be oriented to a frame of reference which does not change depending on altitude or the elevation of the ground, this is so the pilot will be able to judge the angle of the wing through the air flow. If you used angle between the ground and the horizon then it would be constantly changing depending on your height and the elevation of the ground. If the ground level ahead goes up then the angle between ground and horizon decreases, if the ground level stays the same and you increase altitude the angle increases. If you see the angle diminish you would not know whether it was because of a change in attitude, altitude, or ground elevation.

So if the Earth were perfectly spherical pitch with respect to the horizon and ground would be the same thing?

You are misunderstanding what pitch is. Pitch is related to gravity, not the horizon. The horizon is where the ground meets the sky, and changes depending on the elevation of the ground.

The "horizon" is a fixed reference that will be the same wherever you are flying. It is fairly straightforward to create an instrument for the cockpit that illustrates pitch and roll with respect to this horizon. It also relates to gravity, since gravity will be pointing straight down with respect to the horizon. Pitching up means you are working against gravity, regardless of what the ground below you is like. Humans have a natural sense of "up" and what is "level", which is based on our perception of gravity.
Showing pitch with respect to the ground would be much more chaotic. You would need some way to know what the ground below the aircraft is doing, at any altitude. The relationship of pitch and power would be even more confusing, as pitch would no longer consistently relate to gravity, and therefore no longer consistently relate to power.
Passengers typically like a smooth and level flight. Airliners flying over mountains would have a wildly changing pitch indication, despite flying "straight and level." If an aircraft wanted to fly level with respect to the ground, it would require steep climbs and descents in these areas. Since air density changes with height above sea level, not the ground, the aircraft's performance would continually change as it stays level with the ground.
If a pilot is concerned about hitting the ground, there are many better ways to avoid that. Traditionally, charts and navigation will allow a pilot to avoid terrain. Technology like radar altimeters have also helped, which shows the pilot how high they are above the ground. Newer systems allow things like synthetic vision if the terrain is not clearly visible.

Might be worth pointing out that planes might have a difficult time flying if you kept pitching up and down to stay level with the ground...  I think the constant adding and removing of kinetic energy would catch up with you eventually.


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Are carbon fiber/composite aircraft at greater risk from lightning?
Modern jetliners are protected from lightning by their metal skin. When they are struck by lightning, the electricity almost invariably travels through the skin and out the other side without damaging the internals or passengers.
While carbon fiber is electrically conductive, I have not been able to find any resources with a direct comparison between it and aluminum. This forum post would seem to suggest that it is less conductive, mentioning that

Although partially conductive, carbon fiber materials, and carbon fiber masts, are regarded as non-conductive (nonmetallic) for the purpose of this technical information report. For lightning protection, carbon fiber masts require the addition of an air terminal and primary conductor as described elsewhere in this technical information report.

Is carbon fiber as electrically conductive as aluminum, and if not, does this pose a problem in the event of a lightning strike?

I agree with the answer from ymb1, but I think that the underlying rationale would be useful to add as well.  I've looked into lightning strike protection a little bit for a small helicopter design project I worked on and am drawing from that and a useful article from Composite World (http://www.compositesworld.com/articles/lightning-strike-protection-strategies-for-composite-aircraft).
Insofar as I understand it, lightning is always attempting to get to a ground (i.e., to the lowest potential state possible), and an airplane provides a possible location for leaders (some explanation here: http://www.srh.noaa.gov/srh/jetstream/lightning/lightning_max.html - the gist is that you get an electrical channel forming from both endpoints when you have a lightning strike) going from the ground to the cloud or vice versa to form -- and at a much closer distance to both, increasing the possibility for a strike to occur with the aircraft in the middle of it.  This is especially true for airplanes with metal or otherwise conductive skin, such as carbon fiber.
With respect to the question asked, I think that the relative ability of carbon fiber to conduct electricity is a tricky one to answer and is, perhaps, too simplified.  Composites are those wonderful materials that can be formulated just about any way you want to give whatever properties you want.  For example, a representative sample of the carbon fiber material from the tail boom for my model airplane is going to behave incredibly differently when compared to a sample of the carbon fiber material on the leading edge of the space shuttle.  Each has been weaved in the different way, fibers are in different orientations, different additives have been thrown in, perhaps even additional or different fibers have been added to obtain different desired structural or electrical properties, flame resistance, or corrosion resistance.  Hence, saying whether or not a carbon fiber airframe is more conductive than aluminum is not really a straightforward question.  The important thing, though, is that it DOES conduct electricity and that can be problematic.
Hence the importance of lightning strike protection (LSP) measures.  If you don't have an LSP system, your skin becomes the route upon which the electricity can travel, causing damage ranging from burned off paint to scorched skin material to holes burned in the airframe to delaminated composite members.  What LSP does is create an alternative, low-resistance path for the lightning to follow between entry and exit points in an effect to plan where your damage is going to be and mitigate it.


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What is the purpose of the little eyebrow windows on the Boeing 737?
Anybody know what these windows were used for?

From Wikipedia: Boeing 737:

Most 737 cockpits are equipped with "eyebrow windows" positioned above the main glareshield. Eyebrow windows were a feature of the original 707 and 727. They allowed for greater visibility in turns, and offered better sky views if navigating by stars. With modern avionics, they became redundant, and many pilots actually placed newspapers or other objects in them to block out sun glare. They were eliminated from the 737 cockpit design in 2004, although they are still installed at customer request. These windows are sometimes removed and plugged, usually during maintenance overhauls, and can be distinguished by the metal plug which differs from the smooth metal in later aircraft that were not originally fitted with the windows.

Boeing has also determined that removing the windows reduced the cockpit noise by about 3 decibels. The newer models have 10 vortex generators above the cockpit where the windows used to be. It also reduces maintenance costs.

"Better sky views if navigating by the stars" is a little nonsensical. Actual celestial navigation is done with a sextant, not by looking at stars through a window.  I think the origin was for aerial refueling, where the receiver could use those windows to see the tanker. And from there they were carried over to the 707 and 727 as discussed. But without the AR mission, they were pretty useless & just let sunlight in where it wasn't particularly desirable. Eventually Boeing caught on to what pilots all over already knew full well.

@RalphJ Luckily I didn't write the Wikipedia article, I can't refute the claim though, the sextant needs to see both the horizon and a known star. Either way I think the issue was also visibility in turns, or while waiting to take the runway to clear the pattern. The newer 737's have larger windows to improve visibility. I've never sat in a 737 cockpit to say visibility was good/bad to really make an educated comment on it though.


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Can I leave my smartphone turned on in the checked-in luggage?
For obvious reasons, that's the best way of tracking the whereabouts of my luggage. Once the plane lands, it would establish a 3G connection, and I would be able to access its GPS position.

Aside from this being more for travel.SE, your GPS receiver won't do you much good shielded in a closed bag and probably covered by a building (airport) or other bags (transported from plane to airport). I know that isn't your question, but I don't think that is a very good way of tracking lugagge.

i read about a device sometime back, which does the same thing, i.e. keep track of your luggage. you might do a google search about it.

There are apps that will turn airplane mode off at a particular time. Probably best to give it plenty of leeway in case the flight is delayed

Lithium-ion batteries in the cargo hold are a big no-no...

Your phone must be in airplane mode whether it is in the passenger cabin or cargo hold.  In this case the phone will never establish a 3G connection and won't meet your desired use case.
Leaving the phone with cell service on will likely also not solve your problem.  Cell phones tend to use a lot of battery trying to connect to a tower when there are none in range.  By the time you land your phone may have already shut down from losing power.  If the bag is lost it may be deep in the bag handling areas of the airport or some other corner with no cell service and certainly no GPS signal.  In all likelihood unless someone mistakenly takes your bag home and decides to charge your phone and turn it back on this plan of yours will not work.


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What is the lighting technology behind the Dreamliner's dynamic interior lighting?
The flights that I've been on in the Dreamliner (and also Virgin America), have dynamic overhead cabin lighting that provides nice mood lighting, helps alleviate jet-lag, and is otherwise very pleasing to look at. What is the technology behind this? The closest technology I've seen that can offer dynamic light coloring is phillips hue lightstrips.

Although the Hue light strips are the main domestic commercial product, it's pretty easy to get (at an industrial level), lots of different types of LED, and to make your own controller system

frankly, that lighting seems really annoying, and I can only imagine it might be useful based on which color zone you might be sitting in.

I've linked to your question here

This 'mood' lighting is offered by Boeing in 787 and Airbus in A350XWB (as an option) and is achieved by using Light Emitting Diodes (LED). According to Airbus,

Airbus is applying the latest technology in energy-efficient LED (light-emitting diode) mood-lighting on the A350 XWB. This enables the cabin ambience to be tailored to each airline’s own identity, as well as mimicking natural sunrise and sunset illumination that helps the body adapt to jetlag on long-range flights.

The main advantages of LEDs over conventional lights are,

The LEDs are longer lasting (~50,000 hrs).
They are more energy efficient.
They generate less heat.

Phillips seems to be involved in the development of lighting systems for the(se) aircraft. According to led-professional.com,

Philips Lumileds provided the LEDs while Diehl Aerospace engineered the overall lighting system for the Boeing and Airbus cabin interiors.

The light intensity and colors are decided by the airliners and are pre-programmable (and can be changed remotely). According to Bloomberg,

The Finnair A350 cabin has two dozen light settings, aligned with stages of a long-haul flight. It will also feature warmer, amber colors on flights arriving in Asia and cooler “Nordic blue” hues when flying into Finland. ...
  Virgin Atlantic has five primary color periods on its 787 flights: rose-champagne for boarding, purple-pink for drinks, "amber" for dining, another for the pre-sleep period called “work-rest-play,” a silvery glow for overnight sleep, and a waking color.

Similar lighting systems are also offered by third parties for other aircraft.

According to Boeing they are using High-intensity discharge (HID) and light emitting diode (LED) lighting almost across the board on the plane.

The 787 has replaced virtually all cabin, flight deck and exterior lighting with HID and LED lighting technologies. Because these light types have no filament, the operational life of the lights is dramatically longer than that of an incandescent bulb.

The lights you show specifically are most likely tri-color LED's or some other similar array that would allow color selection and combination in a nice package (this is just my engineering assumption/how I would design it).
Once Boeing identified what light ranges relaxed people/helps jet lag the engineer would simply have to spec out LED's capable of delivering light in/at that spectrum. If they chose to use a tri-color package or single frequency LED's is up to them, the end result will be more or less the same optically speaking.

I hope they're not using HID for interior lighting! That sounds painful.


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What are these aircraft? Seen in silhouette over Palm Springs

Screen capture on iMac, of photo posted and claimed taken 11/21/15.
Palm Springs, CA

DC-3 x 2, a.k.a. C-47.

Looks like two Douglas DC-3, the one on the right being the military version known as the C-47 "Skytrain".

Source: Adrian Pingstone

Also to add, the C-47 in the picture in the question and the one above have the European theatre paint.

Gotta love the ol' Gooney Bird ;) one of the earliest airliners to still be in commercial service...if not the earliest.

@SMSvonderTann, the black and white stripes were added specifically for the invasion in Normandy (to reduce risk of friendly fire as aircraft of many different types, paint schemes and insignia were involved).

What I found interesting was that the roundel bars don't have any red on them. The red,white and blue bars on the roundel didn't come in until 1947. Originally it was just a star in a circle with no bars; the bars were added because a different shape made them easier to identify.  https://en.wikipedia.org/wiki/United_States_military_aircraft_national_insignia


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Is the wingtip fence as effective as the winglet?
My guess would be no because it does not reflect the air as well.Wingtip fence
Winglet
What I am basically asking is does the wing tip fence have the same amount of drag reduction (wing tip vortex) as the winglet?

@Ethan, you may want to consider doing a bit more research (either searching here, or searching the web) if you don't want people to downvote or vote-to-close your questions.


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Where is the first Boeing 747-8 ever built stored at today?
I have tried many different ways to try to find where it is stored, but have had no luck.

Looks like it's currently 'stored' on the ramp at Luxembourg International Airport, after landing there on its most recent flight in from Calgary yesterday evening. As aeroalias said, it's in cargo service for Cargolux Airlines. If you want to see where it is at any given time, you can just look up the tail number on flightaware or some similar website. The tail number of this particular aircraft is currently LX-VCA.

The first 747-8 built was not a protype, but a production unit. The first delivered aircraft in both the versions (747-8i Intercontinenal and 747-8F Freighter) are in service, the Passenger version with Lufthansa and the cargo version with Cargolux.
The first 747-8 customer was Cargolux for the 747-8F version.
The first 747 ever built, 747 RA001 'City of Everett' is in Museum of Flight in Seattle.

References would be useful if possible


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What is the height of the Boeing 747-8 landing gear?
I can never find any information about the height of the landing gear on any airliner(can you put it into feet and inches).And Is the height of the 747-8 landing gear around the same height as the 737 or airbus a320.

To compare:
The 747-400 gear is 1.91-2.47 meters tall, depending on model and loading, so it sits slightly higher in general than the 747-8.
The A320 (including neo) sits at 1.79-1.95 meters, so basically the same as the 747-8.
The 737 sits lower than the other two models, at 1.1 meters for the classic models, and 1.2-1.4 meters for the NG models.
It is interesting to note the similarities and differences. Designers want to keep the gear as short as possible to save weight, as well as to make maintenance or emergency evacuation easier. The gear still needs to be high enough to allow the aircraft to rotate on takeoff without striking the tail. Other aspects can be adjusted to maintain clearance for the engines. So even though the A320 and 747 are very different in size, they have the same gear height.
The 737 is different when it comes to gear length. The original 737 had engines that required much less height to clear the ground. The new engines on the classics and NG series needed more room, resulting in longer landing gear. However, the gear is still shorter than the other examples.

Have you noticed with the crj's how the front landing gear is much shorter than the back.

Yes, and the NG does that a bit as well.

Not as noticeable on the NG

In general, the landing gear height is defined as the distance between the ground and the conjunction between main gear strut and the aircraft structure (fuselage, wing, nacelles, etc.).
The landing gear height of any aircraft varies depending the loading conditions and where you measure it (nose or main landing gear). This info is from the 747-8 Airplane Characteristics for Airport Planning document by Boeing.

Image from 747-8 Airplane Characteristics for Airport Planning by Boeing
Here, 'E' gives the height of the (main) landing gear attached to the fuselage.

So the landing gears height is 1.75 meters.


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Do aircraft owners need to purchase insurance?
As far as I know, most (or all) airplane owners purchase insurance that covers liability, if nothing else. Good idea or not, is aircraft insurance legally required in the US, in the way that automobile insurance is required?

Aircraft insurance for personal aircraft is not legally required by any part of the US FARs, nor to my knowledge is it required by any state government, though I'm only familiar with New York in that regard. (As you'll note from the Wikipedia page you linked to, not all states require automobile insurance either, though most do now...)
Aircraft insurance is most directly comparable to marine insurance.
It's generally required by:

Your lender (if you didn't pay cash)
They want to be sure you have hull coverage so if the plane is damaged they still get paid.
Your FBO or Airport Management.
As a condition of having a tiedown/hangar most FBOs require some form of liability insurance in case you taxi into a building or another plane.
Good old-fashioned common sense.
A light piston single is unlikely to take out a building, but if you have an incident costs can rack up fast. Having someone else to step up and pay those big bills is beneficial.

This is how I understand it as well, but I think that it would be silly to not have at least liability insurance with the potential damage that can be inflicted during an aviation accident.  Hull coverage should be a financial decision made in a manner similar to any other type of insurance!

@lnafziger That's basically how I look at it too - If I were a billionaire and could set aside $1M as a liability bond for my little Cherokee I would do that instead of insurance, but I'm not that rich. Hull insurance I look at this way: "I like having my own plane. If $DEITY forbid I wreck it, I would like to be able to get another one. As I pay down my loan the hull payout becomes an increasingly sizable down-payment..."

Yeah, I actually know of a guy who owns a Lear 60 and doesn't keep it insured.  If something happens, he said that he'll just buy another, lol.

If you participate in competition aerobatics, the rules require a certain amount of liability insurance.  I know this is an extreme edge case, but thought I'd mention it.

@DanPichelman I assume if you're instructing for Acro there's probably similar requirements (if not it certainly falls in the "Good old-fashioned common sense" bucket :-) - Is there a specific FAR that requires this, or is it by the competition organizers?

@voretaq7 Insurance during competitions is required by the governing body of the sport in the US.  I'm sure it's the same in other countries, but cannot back that up.  To the best of my knowledge, the FARs don't mention insurance.

Apparently at least the state of Minnesota requires you to have liability insurance only during the period of contemplated use or operation of your aircraft: $100k per passenger seat liability for passenger bodily injury or death and for property damage; $100k for bodily injury or death to each non-passenger in any one accident; and $300k per occurrence for bodily injury or death to non-passengers in any one accident.


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Does transport-type certification account for engine separation and its possible effect on hydraulic lines?
This question is inspired by the United Airlines Flight 328 where the No. 2 engine is damaged.
Some multi-engine aircraft are design to withstand the detachment of an engine while some are not. Boeing 747 is designed to operate after an engine detaches from the pylon. In 1993, Japan Airlines 46E successfully landed after the No. 2 engine detached from the aircraft (1) In El Al 1862 and China Airlines 358, the detached engine struck another engine. Those are outside of the design scope. On the other hand, the detachment of an engine on a DC-10 would sever hydraulic lines to the control surface as in the case of American Airlines Flight 191.
Many twin engine aircraft are certified with ETOPS so that in the event that one engine failed, the aircraft can return to an alternate airport within the certified time span. However, the ETOPS scenario listed by FAA only includes engine shutdown but not engine separation. (2)
Are there any twin-engine aircraft that are controllable after an engine separation?

Unsure whether it is designed to withstand an engine separation, but Boeing 737 seems to have an engine separation memory items:
https://www.johanpercherin.info/airline-pilot-training/boeing-737-memory-items-engine-fire-severe-damage-or-separation/
And 777 has one as well:
https://www.theairlinepilots.com/forumarchive/b777/b777memoryitemsandlimitations.php

Really, as long as it didn't damage the wing box structure and take out all the systems, you're probably ahead of the game to have it fall off.  Significant drag reduction.  Imagine the range improvement!  With tail mounted engines, you are probably going to be spot of trouble, and at minimum even if you can control the thing, you will be having to land REALLY fast with the C of G moving that far forward.

Unfortunately, failures of this sort have occurred more than once in the past. There are all sorts of failure effects mode analysts studies done on aircraft systems. Critical areas and failures such as the one described receive a lot of attention.
Their is also a process where by a sentinel event (an accident) is heavily analyzed to determine the root cause. If a statistical safety analysis shows that the aircraft design does not meet the required levels of safety, mandatory procedures or modifications my be imposed. Or, if an aircraft type cannot be economically modified to meet the required levels of safety, it will be taken out of service.


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Why are turbofan inlets circular- or oval-shaped instead of square-shaped?

Source: materialsengineeringconsultant.com and initious.blogspot.com.
Most of the engines are circular except for some that are oval. The oval shape provides a better ground clearance.
Why aren't the intakes square-shaped? Is there some aerodynamic reason for the circular / oval intake shape?

Why so many down-votes for this question? By the way the two current answers provide interesting details showing the question is a good one.

Here are some more discussions: https://www.reddit.com/r/askscience/comments/228tuk/why_are_fighter_jet_air_intakes_square/

The main purpose of having a square inlet is to have an oblique shock at the entrance so as to decelerate the air to subsonic speed before reaching the compressor. Also, the square inlet ramps are adjustable to produce optimum shock systems over a wide speed ranges. However, they are quite complicated.
The turbofans used in civil airliners operate at subsonic speeds and don't require any shocks for flow deceleration. The circular shape is the best for getting maximum amount of undisturbed airflow into the engine, especially the bypass section. The inlets of high bypass turbofan engines are simple, straight and short with a thick lip.


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Is a swept wing the better option against the winglet
I know that the swept wing decreases lift and the winglet increases lift. Is it better to have a winglet or a swept wing.

Swept wing and winglet are not used for the same purpose, please search before asking: swept wing and winglet.

Both ideas are dealing with different physical phenomena, so there is no "better or worse" as they are, actually, sometime complementary.
Swept wing is used in high subsonic (Mach > 0.7) airplanes, and the idea is to reduce the effective incidence Mach on the airfoil, reducing the negative effect of compressibility on the drag.
However, the winglet tries to reduce the negative effect of having a finite wing as the air in the tail generates a vortex which increase resistance. In summary reduces what is called "induced drag".
So... low subsonic airplanes might have winglet and not a swept wing (notice that this one is trapezoidal):


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How does a hot tip-jet supply fuel to its engines?
Some tip-jets move their rotors by running jet engines on each end of the rotor. Obviously there must be some ways to supply fuel to those engines through a rotating body. How is this accomplished?

There are pipes inside the blades which connect the engines to a rotary seal inside the main rotor head assembly. That seal allows fuel to be pumped into the blades from a port outside the main rotor head. Such seals are used in a variety of mechanical engineering applications where a fluid, usually lubricating oil, has to be provided to a rotating piece of machinery.
One example which you can probably find a cross-section of on the web is the method of using oil under pressure to change the blade pitch of a constant-speed propeller.

Would you mind to elaborate how a seal is accomplished in the main rotor head?

as a simple example, imagine a round shaft with a shallow groove cut into it. the upper and lower edges of the groove are fitted with O-rings. Between them, a hole is drilled in the groove into the side of the shaft reaching to its centerline. Then another hole is bored down the axis of the shaft to intersect the first hole. the shaft thus fabricated is set into a hole in a solid block with a hole drilled through its side coincident with the groove location on the shaft. if oil is pumped in through that hole, it fills the groove and flows in the first hole in the shaft and up the second hole.

I never understand people's description of mechanical things, but the example in your comment is very well written and easy to understand.

@WayneConrad, thank you for that. For a short while in my previous lifetime I was a technical writer, so I guess it paid off!


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How does Pitot Heat influence airspeed indication (assuming no ice or moisture)?
Should Pitot Heat ON (in dry weather conditions) decrease airspeed indication because warmer (so less dense) air flows through the tube?

No, there is no decrease or change with the use of pitot heat.
The pitot system measures pressure. There is no airflow through the system in normal operation. Any airflow through the system would be due to a system failure which led to leakage.

Pressure is proportional to temperature...

@Notts90, no, it isn't. There are complex relations between pressure, temperature and density that depend on which variables are fixed by external conditions and they are totally irrelevant in this case, because the variable fixed here is directly pressure, specifically the stagnation pressure of the oncoming air, and that air is not heated (yet), so its pressure is not affected (if it was heated, its pressure would be lower, as the question correctly states, but it is not yet).

@Notts90 You are correct insofar as concerns a fixed volume system, which the pitot system is not.


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What will be in 'radiotelephony privileges' part of EASA PPL without practical RT examination?
My question is addressed to pilots who recently obtained PPL in Europe (preferably in Czech Republic, but not so important).
As I understand, EASA itself does not require separate radiotelephony license (FRTOL, RT etc.), but some EU states does.
Does anybody have any recent experience in obtaining EASA PPL in Europe (especially if it is not your domestic country)? What do you have in the 'radiotelephony privileges' part of your license? Have you had to pass a separate practical RT exam?
NOTE: I do not consider UK.

At least I got my own license (Czech Republic CAA), and I have "English VFR only" in my "Radiotelephone privileges" section. It is not English proficiency mark (just because I have "ICAO English level 4 valid till..." in "Remarks" section). As I understand, some countries still require separate RT license, but my question was about privileges stated in PPL.

what do you mean "radiotelephony privileges"? The PPL itself doesn't allow you to use radio at all (legally - you shouldn't be even listening to the traffic).
You have to get a separate "Flight Radiotelephony Operator's Licence" issued by any member state (usually issued by the telecommunication regulator).
For each state - you should contact any aviation school / club and they should help you at least pointing out the direction (or giving out some training). This way I got my radio license (aviation RT operator) even in non-domestic country.

EASA PPL itself contains "Radiotelephony privileges" section (as I know, XII), and something should be specified there (for example, "English, VFR only"). If it is, for the most states it is enough without separate RTOL.

I believe this is older one, but lets check https://upload.wikimedia.org/wikipedia/commons/7/78/PPL%28A%29_Lizenz.jpg   (I am learning, but I had to do the RT exam separately)

I see what the "English" is. It is often used in countries where English is not used very heavily (CZ, SK, HU, ..). In their PPL it's mandatory to have ICAO English level 4 to fly abroad. Though I believe they still need a licence of the "limited radio operator for aviation service". It is not so difficult exam

Thank you for your try, but I asked just about license, not about RT exam or requirements. Generally if you have "RT privileges" in the license, almost all members does not require separate license (but a few still does), and my question was not about "how to obtain RTOL" or "who requires RTOL". I asked about "RT privileges" section of freshly-issued EASA PPL and whether the holder obliged to pass RT practical exam.

As I understand, you attached JAR (old) license sample: I suppose that "RT privileges" exists in EASA version, but I also do not know exactly

Please do not assume. The reason is that there are different licences from different regulators. I really had to do the RT exam separately. I believe the answer for your different post is wrong.

I kindly ask you to return here and add the info after getting your EASA PPL (and issued state, if possible). I suppose that you are not training in UK, and also you are going to obtain EASA one (not national). Will highly appreciate it!

Let us continue this discussion in chat.


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Dropping an object from really high, landing at 0 velocity due to 'free' reverse thrust
So a friend had an 'idea' where you could make an object land with 0 velocity.
Basically the idea is that you drop an object (like a rocket shape) from some altitude. To the object you attach fins (fixed propeller blades so to speak.) as it falls it starts rotating, due to the attached fins.
Now at some altitude above the ground you either:
1) You rotate the fins to get reverse 'thrust' (you don't really have thrust, but you would slow down rotation.)
2) Retract the fins and expand new ones that face the opposite way (so they counter spin)
3) something along those lines (like extending flaps)
Now one of the arguments he had as to why this works is because you could expand larger fins for the counter rotation, therefore getting more drag and generating more 'lift'.
It feels like you cannot do this, but I cannot give a (good enough) reasonable explanation as to why it would or would not work (I'm a noob in this area.) So let's ask the people in the know... that's you.
I would love to see some 'proof' more so than speculation.
Thank you in advance.

I should have added that the system cannot have any energy added to it, so the mechanism of expanding the fins, or whatever other mechanism, should come from the energy gained from the rotation.

This question is simply about energy management in a < 100% efficient closed system and not aviation and therefore belongs on Physics.SE.

I vote to migrate this to physics.se

I'm voting to close this question as off-topic because it belongs to Physics.SE

Come to think of it... Ever seen a maple seed?

Now if only I found a migrate button

What you are describing is similar to a helicopter autorotation.  That is something that does work.  The rotors both generate drag and store rotational momentum.  Then, some of the momentum is converted to lift for landing.

Or an autogyro/gyrocopter: https://en.wikipedia.org/wiki/Autogyro

Autorotation requires forward speed; the question refers to dropping the object.

@DavidRicherby, sustained autorotation does require forward speed, but the final flare does not.

@JanHudec I think you may have that the wrong way around.  I can autorotate all the way down with zero, or even negative forward speed, but I do need some to flare?

@Simon, by "flare" I mean when you pull on the collective at the end to arrest the descent. That shouldn't need forward speed, does it?

@JanHudec The "flare" is pulling back on the cyclic to convert kinetic energy (speed) into rotor RPM so that you can next use collective to increase pitch.  If you do not flare at the bottom, you will hit the ground hard since there is not enough energy stored in the rotors to arrest the rate of descent.  Without forward speed for the flare, you will crash in an autorotation from above hover height.

@Simon, I see. The device in question could have a flywheel to have more energy in the rotation and thus do without this part though.

@JanHudec Nope.  The flywheel cannot be 100% efficient so will also lose energy, meaning that it will take more energy than it can give back.

@Simon, nobody needs the same amount of energy back. At the final position, the device will have much less (by $mg\delta h$) energy than it had at the point of release. What it needs to do is dissipate that energy in a controlled way. A controlled way that is very similar to what autorotating helicopter does.

Given the object has a terminal velocity, it should be possible.
Before it hits the ground, it has a speed no greater than terminal speed.  Assuming it has some sufficient propeller system, it will require a finite amount of energy to slow the descent to zero at the altitude desired.  But since the start point is arbitrarily high, we can collect an arbitrarily large amount of energy from the fall.
Imagine a quadcopter with depleted batteries and some sort of charging system that can be driven from the rotors.  Drop it from a height and let the descent charge up the battery.  Then a few feet before the ground, turn on the motors and let it hover.
Now this example uses batteries and electronics, but the argument doesn't change in character if you turn it into a kinetic spinning rotor instead (it's just harder to build).

It cannot be zero terminal velocity because it means a 100% efficience in loading the free fall nergy and 100% efficience in transforming that energy in lift

This will not work.  You must think in terms of systems and the total energy in them.  Without adding energy from outside the system, the energy in the system will always reduce.  Charging the batteries takes energy from whatever is producing lift at less than 100% efficiency.  The lift generators themselves lose energy through drag, friction etc.  With a system such as yours, the total energy decreases rapidly and will be very much less than when you started (with nothing but potential energy) and you cannot "cushion" your landing.

@Simon, why is 100% efficiency required here?  It's not.  The drag during the fall means the kinetic energy that has to be corrected near the ground is only a fraction of the potential energy available at the beginning of the fall.  If I can extract just that fraction, I have sufficient energy to stop at the bottom.

@jean, Nothing in the answer should suggest that it has zero terminal velocity or 100% efficiency.  Neither are required.  It simply has to have some drag (and therefore a positive terminal velocity).

A small positive terminal velocity is ok but also note drag is "stealing" energy from the fall and it's energy you cannot store. Drag itself is not 100% efficient meaning just a fraction of the energy its subtracting from the fall is actualy used to slow dows the velocity.

@jean, correct, but entirely sufficient in this problem.  If we wanted to end the exercise at the original altitude, the lack of 100% efficiency would prevent us.  But since we want to end the exercise on the ground, we can throw away tremendous amounts of energy to drag and still succeed.

Yeah but that's a answer for how a parachute works not for OP question =)

@BowlOfRed It is a closed system.  What will you convert the kinetic energy into to come to a safe stop?  You cannot gain any energy, and you cannot store it 100% efficiently.  Therefore, you will have less stored energy available to stop the descent than has been converted from potential energy into kinetic energy.  There is one simple rule, you don't get anything for nothing in a closed energy system.

The same thing that a running quadcopter converts the energy in its battery to: air motion and eventually heat.

How is charging the quadcopter batteries different (in principle, of course) from a "porpoising" descent in a sailplane?  You start level at say 10K ft, dive to 9K, climb back to 9800 ft (going through a nice 0g at the top of your climb), and so on, converting potential energy to kinetic and back again, with of course some loss at each step.  With the quadcopter, you convert some of the potential energy of height to electrochemical energy in the battery, then recover it.

This reminds me of the defunct Roton experimental rocket, except that it had helicopter rotor blades powered by rockets at the tip to take off.
It could be achieved with just one set of blades that have a very large pitch range adjustment. Pitch the blades downwards on descent so that they'll spin like a windmill and let the angular momentum build up, then pitch the blades upwards to convert the angular momentum into lift. The rotor system would require a flywheel of some sort to store the momentum needed to slow the craft down by a decent amount.

As it is this post should be a comment, not an answer. However the content is very interesting, so you should try to make it a full answer before it is closed as "not an answer". Welcome to the site, I hope to read many good questions and answers from you.

My apologies for posting a question that was 'off-topic'. In any case I want to thank all the people who replied. While going through the answers I read up some more about some terms people used, which led down to a late night reading many interesting things. So I learned a couple new things, which is always fun. Thanks again for all the replies.


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What risks come from passengers taking baggage during emergency evacuation?
In recent news, the pilot of an aircraft that caught fire was chastising passengers for taking their luggage.
What are the major concerns behind his criticism?
I like to put this in context:

All passengers and crew survived.
There were no injuries.
Crew reported that the evacuation was very orderly and efficient.

So what could be the reason for the pilot speaking out so critically? So critical, in fact, that he argues that overhead-compartment doors should lock between takeoff and landing. My guesses include:

another passenger cohort could have been less orderly, and pushing with luggage resulted in injuries or people becoming trapped.
sliding down inflatable exit slides with luggage could cause the slides to puncture and trap other passengers.
the inflatable exit slides are not rates to carry the weight of an adult + luggage (seems unlikely unless the adult is massively obese).

Would appreciate hearing a list that is not just educated guessing.

If you are standing up in front of me to get something from an overhead bin, you will not be standing up for long.

There were injuries in that evacuation, though I don't know if any of them were related to people taking luggage with them.

@Simon indeed... I am flabbergasted that other passengers let those idiots take their luggage with them (well, that and I haven't read about the pax being prosecuted).

While the (second) last thing you want is passengers taking their luggage with them, the (very) last thing you want is for fighting then to take place as other passengers try to prevent it happening.

@user5505 thank you for the sanity.  I can't think of a better way to make a disaster worse than to instruct a culture of aggression during such times. Fine line between looking out for yourself, and causing others' injury (and potential death from trap/trampling)

I'm not sure where I read it (perhaps pprune?), but I saw a good point on how the companies treat the passengers after the evacuation. If you're left alone in the airport, without your wallet and some clothes, and nobody gives you food, hotel, water, phone calls... you probably will advise everybody to get your things in an accident. If I were a company, in the safety instructions, I'd say that passengers would have access to X and Y and Z in case of problems like that.

@NewAlexandria Sanity? I never advocated fighting, but if you are between me and an exit whilst you try to gather belongings, I will go past/over/under/whatever it takes. The person grabbing the bags cares nothing for others. What sanity are you referring to? People will have been delayed in that evacuation by others being selfish. If the wind was stronger, or from a different direction or the tanks half full, we might have been counting body bags instead of lucky stars.

@NewAlexandria Read the first sentence of Lightsiders reply.  There is no-one in the aviation industry who would disagree with that.  Why do you think that is?  So that they can incovenience the evacuees?

If 30 of the passengers spend 3 seconds each picking up luggage on their way out, that will add 1½ minutes extra to the evacuation time. Needless to say, that's not a good thing in case of a fire.

@leo Just to be fair: grabbing luggage is something that happens in parallel, not in sequence. In a normal airplane with 3 chairs per window you would thus have 3 stages, so if every passengers spends exactly only 3 seconds more it would only add 9 seconds to the evacuation. Realistically however it's far more than 3 seconds, as both grabbing them takes longer and walking through the aisle with them will be a lot slower.

Gents, talk of times added to an evacuation is neither possible nor useful. The Manchester Airtours disaster is a case study. I forget the exact time but it went from survivable to deadly in about 20 seconds as the hull was breached by the fire and smoke poured in. If that evacuation had been 20 seconds quicker, more (all?) would have survived.  In this particular case, deciding to vacate the runway was the main cause but the point stands.  Adding ANY unneccesary time to an evacuation in case of fire is potentially deadly and delaying, even for seconds, to collect belongings is inexcusable.

As soon as there's a fire on board, the absolute top priority is getting everybody out as soon as possible. Aircraft are designed in such a way that, even after a crash landing (or other serious malfunction), the passengers will have a minute or two to evacuate before conditions in the cabin become toxic (fire, smoke, etc); this is done by using flame-retardant material and burn-through protection, but in an intense fire these won't protect the cabin for long, and once they fail no-one will be able to survive inside the aircraft for much longer than that. Smoke inhalation and oxygen deprivation kill just as effectively as being burned.
Therefore everyone has to be able to evacuate from the plane within 90 seconds, even assuming the plane is packed to the gills with passengers, and half the exits are inoperative. Given that the aircraft may be damaged after  a rough/crash landing, some of the doors may be unusable (due to fire or smoke just outside them), it may be dark in the cabin, and people may be injured and/or panicking, it's vital that nothing slows down the evacuation. To get an idea of what a 90-second evacuation of a fully-loaded aircraft looks like, see the video of the A380 evacuation test - and these passengers were calm, uninjured, and prepared. If passengers take hand luggage with them this is slowed down:

The time it takes to get it out of the overhead bins (with everyone else crushing against you to get out).
Carrying the luggage down the aisle (without tripping, hurting yourself or anyone else - again, look at the A380 video, and imagine trying to do that with a suitcase). If you lose your luggage, everyone behind you will have to climb over it to get to the exit.
Maneuvering your suitcase around the corner to the door, not getting it stuck on the door frame, with people behind you literally shoving you out the door.
Plunging down a very steep slide the height of a two-storey building (or more, in case of the A380's upper deck) at high speed, with your suitcase flailing around. At best it whacks you on the head, at worst it punctures and deflates the slide, which given the crush of passengers behind you will probably lead a few people to plummet from the aircraft doors straight to the ground.
Assuming you've made it to the ground, there is someone else plunging down the slide right behind you. If your suitcase slows you down even a little, they will plow right into you, and soon you'll have a crush of people at the foot of the slide.

In this specific case, the fire was fortunately not serious enough to defeat the cabin fire protection before the last passengers had evacuated - but as @Andy said, there are unfortunately other examples where the passengers were not so lucky. To illustrate the risk of fire after landing: Air France Flight 358 ran off the runway at landing, and despite having little fuel on board, the resulting fire completely destroyed the aircraft; luckily, everyone evacuated in time. Once there's been a major malfunction, there is no way to tell how much time you have left to get out - fire can spread very very quickly - and so you have to get out as quickly as possible. Taking luggage with you endangers your life and that of your fellow passengers.

Holy cow!  That evacuation test video was incredible!  I'll have that in my mind next time I'm sitting in the back of the plane waiting for those lazy smucks near the front to get their luggage and exit so I can stretch my legs!

@CortAmmon Agreed, incredible!  But (only?) one injury even under a near ideal test.  I would hate to be that person...

While impressive, the real times will be way longer if you account for stress, disabled people, not everyone being an athlete, obese passengers, etc. I would be very, very curious to see a test done with a proper statistical sample of people who fly (age, physical abilities, etc.). Even without the stress factor I am sure it would be less way optimistic.

The evacuation tests are done with a reasonably representative population sample (x% over the age of 60, y% carrying pillows simulating infants etc). Obviously airplane manufacturers will give their test the maximum change of success and tend to pick more athletic candidates, but the airworthiness authorities monitor these tests closely to ensure they are representative.
The point if not whether 78 seconds is a realistic evacuation time - the point is that an aircraft evacuation is very stressful and anything which causes delays could be dangerous.

Just one angle I would like to add to these excellent answers.
Passengers might be slow to get off because they want to retrieve their passports, driving licences, phones etc. This could well result in people at the back losing their lives as explained in the other answers on this post.
But consider this: if people are on the aircraft, the fire service can't properly attack the fire, because covering the aircraft with foam might SUFFOCATE the passengers still on board.
So if passengers are quick to get off, the fire service can then deal with the fire as quickly as possible, and it might well result in your driving licence being saved as well, rather than you die along with your driving licence.

Comment on the "automatically locking overhead bins": I doubt such a system will ever be installed. Systems which have to work after an airplane crash are brutally difficult to design, and tend to expensive and heavy. Airplane crashes are fantastically rare, so for most planes, the system will never be used, and the more an aircraft weighs, the more it costs to fly.

Items that valuable/useful are best kept in your pockets anyway along with cash/cards (and if you get bored easily a paperback/kindle).  No retrieval needed then, nothing slowing you down.  But on a more prosaic note even carry-on luggage isn't immune from theft/pickpockets at some airports (especially on arrival), and access to the lockers isn't guaranteed during the flight (assuming you like to read in turbulence).

Besides what Lightsider said about designing such an auto-lock system, do you want to guess how many would be trying to open those very same overhead bins? My guess is that while the number might (for a very liberal definition of might) be smaller than one person per crash, that will still happen often enough to have to be accounted for.

A belt pouch, money pouch (of the kind that many travellers already have) or even just putting the most important items in your pockets is probably a far more reasonable choice for everyone involved.

@Lightsider, it could be locked-by-default, and check a "there's no emergency going on" signal before allowing it self to be opened. I agree that sociologically it would probably add more problems than solve, though.

Get them to lock when the seat belt signs are on...

@Lightsider AIUI the suggestion is for them to lock at takeoff, and that typical crashes (that passengers can walk away from) are not expected to cause the already-locked locks to break.

This doesn't answer the question. The question asks what are the dangers of evacuating with luggage, not what passengers can do to mitigate the problems of leaving documents behind.

@DavidRicherby the question is answered in the first 3 paragraphs, so to me this stays. I would agree though that the last 2 paragraphs are superfluous and should be edited out.

I have taken out the last two paragraphs and will put them here unless anybody objects. ...
I don't know how we can get this across to passengers though, because they won't read this post and it could be a commercial disadvantage to airlines if they scare the passengers too much.
The best suggestion I have heard is having automatically locking overhead stowage, and perhaps also updating the before you fly documentation to say "If you have a problem with this, scan your passport and driving licence and put it on a USB key on your keyring".

I would just like to add the requirement for certification is 90 seconds, which is difficult to achieve in a real emergency even if you don't get a group of passengers going for their luggage. Nobody can tell the fire it has to wait for 90 seconds... You have to get out as fast as you can because you don't really know exactly what's going to happen next in what time scale. Kerosene burns hot - it can burn through thin fuselage skin in seconds and there are tonnes of kerosene on an aircraft.

On some aircraft in some airliners, a few emergency equipement are located in overhead bins along the cabin. Flash lights, extinguishers, first aid box, etc. Furthermore, you won't always crash land near a city. How about survivors in a rought forest crash context unable to access the bins ?

Remember the Manchester airport fire... a major fire on the ground which led to the loss of over fifty passengers, partly due to smoke inhalation.
These days a fire on board has to be taken very seriously. Just because you're on the ground doesn't mean you're safe!
So, in your request for a list, there can only be one item on that list... that slowing down the evacuation can result in very heavy losses. I'm sure every commercial pilot has been briefed on past fires and knows how quickly they can become disasters. The fact that no-one received fire related injuries on a particular occasion is irrelevant.

If I were in an airplane crash (and when I fly I generally have my young children with me), I wouldn't want people to think that it was OK to stop and take their luggage with them.  First, not only does it slow the evacuation (the goal is get everyone out within 90 seconds), but it puts other people at risk if getting the luggage

slows you and the people behind you from getting to the slides,
could harm others if you open it and bags coming raining down,
could cause an obstruction if it gets caught in the aisles under or in front of someone
could damage the slides, and
could cause an obstruction at the bottom of the slide as people are coming out of the plane.

Keep in mind that the BA flight in LV that caught fire wasn't full.  In an emergency, on a completely full flight, on a larger airplane, do you really want people thinking "those other people on other flights took their luggage and everyone survived!" when you and your loved ones are trying to just get out and get to safety? The pilot of the BA flight has a right to also have strong words, as the flight crew is always the last to evacuate.  Delaying an evacuation could prove particularly harmful to them as they can't get out until everyone else does.

I don't see what this adds to the answers posted before it.

It adds a passenger's opinion, giving priority to his family (lives), towards another passenger's opinion giving priority to his bag. And, crews are the ones under the highest risk of death for being the lasts to deplane. That's a psychologic insight about the crew severity of words on this case. Rules are clear, but to understand why they are so strict, you have to get in place of others. Core problem : in extreme situations, instincts takes precedence over reasoning which make you act selfish and only take care of the most valuable for you. Few people follows rules they don't understand.

EDIT : This answer doesn't answer OP's request for the reasons why... However, some people looking for an answer such as the one asked by OP already knows the rules, and agree with it only when there is a critical risk of death.
When you see that slide deploying, just assume one simple principle, even if you don't smell any fuel fume nor see any flame or smoke. Slides aren't deployed for fun. They are deployed because the situation is so critical that the evacuation cost is probably less than any other of the remaining outcome (injured people, deaths ?)

Rules are there for a reason !

There's only one thing that can put an end to the internet bashing over people (if that's the problem) who bring their stuff with them.
Because you can't educate 7 trillion different people the same way (>80% doesn't listen carefully to emergency guidelines) and make all of them suddenly understand their 20,000$ camera is not worth risking one single live (prepare to be sued and you'll spend at least 100,000$ if one died - simple math)

Cabin luggage :

less than 4Kg (8lbs)
under 0.40m x 0.20m x 0.30m (100in x 50in x 76in)
without any sharp component
and with a safe and strong handle.

Then, no problem, everyone can bring his stuff with him upon evac. Simple rule, no possible sueing. You have your (critical) medication, your passport, business documents, credit card or cash, etc.
This answer doesn't really addresses the asked question; however, the asked question is an open and endless debate (pros and con) and have precise answer from the airline industry (NO ! There is no possible compromise when it comes to safety concerns), while mitigated answers from passengers point of view.
As long as you're not in the industry, never experienced a fullpanic emergency situation and lucky enough to get out alive or unharmed, you can't measure the importance of safety rules. That happens everyday : you can repeat passing that red stop until the day you have an accident. In similar cases, the only thing that works in a certain extent is strengthening the rules by removing the problem at the source, instead of trying to fix a design flaw at a later stage : disallows those large luggages in cabin ! Not the most seducing solution, but working (if correctly applied)
Side note : I may blame the crew for their severity, but I won't because I understand. I may blame some passengers with their huge bags (putting those behind at rish because that plane full of fuel CAN explode) but I won't because I understand, they are in panic, or not knowing the rules and aren't aware of anything else than themselves (my point is everyone has his own limit when put in extreme situations - you can't expect from everyone to get 100% prepared for the 987 possible scenarios on each flight while thinking of others)
I'm just both happy noone were injured on this case - EDIT: Wrong ! there were injuries -, and sad the practice has taken a so wide and careless proportion. If that continues, statistically, one big bad thing will happen sometime in the future, for sure.

As highlighted by a comment below the question, there were injuries in this case. One big problem with luggages is the fact that they can be lost anywhere including in front of an escape hatch and thus slow down the evacuation, whatever there shape or size.

@ManuH. I do agree entirely, and I'm a frequent flyer and an aviation hobbyist :) And that's also why I don't believe in impossible solutions : Rules are there, but just a few follows them and that's how it is. People underestimate the risk of a small bag - we both agree just like 99% of us here on AviationEx - but that's how it is, you can't educate everyone. After 9.11, rules have changed, it's one way to find a solution. But we can't jump from a 20lbs cabin luggage to a no luggage cabin on all flights. If you can't educate everyone, you can reduce the risks instead.

There at least one 40lbs cabin luggage per flight on an airline I know well believe it or not, and a few others around 30-35lbs. That airline is black listed in Europe. We still have 10-20lbs cabin luggage allowed even on european and american airlines. Give that to a panicked woman on high heels and we'll head to a disaster. My point is : most people won't care, how well you may argue or explain the rules - I came from several loooong interesting readings about the whole thing, taking each relevant argument from pros and cons (both are) The problem is not where we think it is.

I disagree with something you take as a fact: you can educate every passengers. Methods may be quite different from someone to someone else, but airlines passengers are a few proportion of all humanity, and the demonstration were the more effective on that population when introduced. Since, this population has changed, educational methods may change, but my point is that you can educate people, or at least try.

Thanks for having faith in humanity, thumbs up, honestly. I don't that much, unfortunately (We both know about "impossible" passengers : smells, noises and other disturbances, phone calls, hand bags everywhere, language barrier, the boy that think he's the boss of the airplane, or knows everything about travelling, the one that took your seat, or is mad at everyone because he expected to be upgraded to first...) All that aren't a real problem at all, until something bad like discussed here happens. I was speechless watching the video; I expected much more "educated" people on that flight...

I don't want to look stubborn, but the exercise is to consider the problem from each point of view. Airliners : they are experts of travelling, yet, they don't share your opinion on educating every passenger on every flight because it implies extra costs, and time, for something that may happen once in a billion repeat. Safety demo is cheap (Asked flight attendant opinion from three different airlines) Self educated passengers like me are assuming to be educated enough to follow guidelines, yet, it happens I fail to, or take a few seconds to realize my mistake... diversity of point of view.

As highlighted by these two points of view (pros and cons), there is no clear answer.
In short, in case of evacuation, the aircraft must be empty of passengers in less than 90 seconds, not using all exits (because some may be obstructed by fire).
Given the fact that any luggage in an evacuation process may be lost anywhere from the seat to the tarmac, including the small escape hatches and the middle of the escape slides and cannot be retrieved until the end of the evacuation process, it may constitute a potential obstacle for the other passengers. An obstacle in such a critical phase may lead to at least injuries (broken leg while reaching the end of the escape slide), and in the worst case to passengers not able to evacuate in time.
Keep in mind that there are emergency services on the runway, and insurance if you lost luggage in the process. Therefor, the only thing you should think of is to evacuate to stay alive.

To me this is one of the very clear-cut cases where not all opinions are equally valid: As far as I'm concerned anyone who would defend stopping to retrieve your carry-on from the overhead bin after an incident requiring use of the evacuation slides (fire or otherwise) is a blithering idiot. This is the moral equivalent of waking up to discover your house is on fire and stopping to neatly fold your wardrobe so you can take it outside with you, and making everyone else in the house stand there and watch you fold your clothes.

@voretaq7 so that would place your opinion squarely in the "con" category, with an "I am right, you are wrong" chaser?

@paul Yup. I bet if you go interview the cabin crew from this flight (or any commercial airline) you'll get very similar responses from them. You'll probably also get an earful about people sleeping through the safety briefing and then not knowing what to do...

@voretaq7 I'm quite sure the cabin crew have one opinion. I'm also quite sure a good percentage of passengers have another, and that group also thinks "I am right, you are wrong". Regarding the sleeping through the briefing part - what if they've seen it before? Like on the previous leg in the same aircraft type?

@paul the briefing is not about knowing what to do but about activating the memory. I'm not a neuro-specialist but I'm quite sure the brain works like a computer. If you remind something to someone (put this knowledge in cache), it is quite faster to access to this knowledge, espacially in case of emergency where time is critical. "I've seen it before" means you you it but you may takes tenth of seconds to access to this knowedge. "i've seen it less than an hour ago" means you may access your knowledge quite faster (less than ten seconds). The previous leg may be hours away

@voretaq7 + ManuH:  both sides have stated their positions. The travelling public have clearly said that they are not interested in the pre-flight briefing, and will be taking their bags with them. These same people summarily dismiss your position with prejudice (you guys do know you are in the minority here?). Personally, I like to look over my shoulder and see how many are ignoring the FA. It's usually > 80% and more than one FA has said she feels ridiculous doing the seatbelt demo in those cases. If you want to make their day, ask a question.

@paul The "traveling public" is not an expert body. Trained and certificated flight attendants, the NTSB, the Flight Safety Foundationm and Airbus have made their positions quite clear on this, and they are the experts. If you want to discuss this further you stop by chat & we can get into NTSB reports together.

@voretaq7 expert body (as travelling public) may be wrong. What is interresting is arguments, not where the argument comes from (neither if their side is in the majority or not). The seatbelt demo is near the beginning of the safety demo because unlock it quickly save severals seconds in evacuation and public is familiar with car seat belt whose mechanism is quite different.


text:
what is the statistical risk of head rotor failure?
What are the chances of rotor failure? What percentage of crashes are related to a malfunction of the rotor head?

You are welcome to search the NTSB Accident Database for helicopter accidents with certain keywords. I'm not sure that this is answerable though as the data isn't typically compiled as percentages due to a certain component failure. I'm willing to say though that rotor head failure is insignificant given accident reports I've read.

I've only ever heard of 2, which doesn't of course mean that they are more, but I would say statistically insignificant.  In my experience, the great majority of rotor failures has been the result of something else, e.g. not entering autorotation quickly enough after an engine failure; mishandlng negative G in a helicopter with a semi-rigid head etc.

I worked medium and heavy transport helos in the Marines, and I never heard of an incident caused by a rotor head failure. Blades, transmissions, all kinds of other things, sure, but not main rotor heads.


text:
Why are ejection seats not used in commercial passenger airline planes?
This question may sound a bit strange. But if a plane full of people traveling to their destination goes down, why not drop the seats? Or eject them sideways. Or however. At a height where it's possible for the people to breathe safely. Does the design of a plane forbid this? Is it too expensive? A crash is a rare event, so I can imagine the last. Contrary to a car crash, there is time, before the actual crash, to throw the people out somehow (with a parachute, that is). I know my father would be delighted!

Among other reasons: 1) Weight & cost.  2) A large fraction of crashes happen on takeoff or landing, where the ejection seats would be of little use.

..and the extra weight would mean that more flights would be required to transport the same number of pax, resulting in more of those risky takeoffs/landings.  Fitting ejector seats and parachutes would kill more people than they would save.

Ejection seats would be very costly and heavy. Aircraft are weight sensitive. The more the aircraft weighs, the less weight (people) it can carry. That means, travel would be way more expensive. And, fewer people could travel. They are also violent. Their very use would lead to deaths and casualties. Unfortunately, self bailing out of the aircraft is also not likely. Parachuting is a perishable skill. Regular passengers would not have the skill nor discipline to evacuate the aircraft properly, let alone skydive to safety.